Playing in a setting with just one playbook?

I've been working on a hack for the Stalker/Roadside Picnic setting and I've been thinking about making just one playbook for all the players to use.

The characters will all be Stalkers, who will have different areas of specialty and expertise, but perhaps not enough to make a whole handful of separate playbooks appropriate.

If anyone has some familiarity with this setting from the novel/film/videogames, I could use some suggestions on what separate playbooks would be useful beyond the generic 'Stalker'...

If the playbook had significantly more moves to choose from, it would be possible to have three or four players make characters with no duplication of moves.

Is this a terrible idea?  Anyone see serious problems with it?  My enthusiasm might be blinding me to the downside of this.

Well, playbooks offer insta-niche protection. It doesn't matter that the Gunlugger is better at killing things because the Hardholder runs a whole society and the Touchstone is a beacon of hope.

If you have two Gunluggers, then the one who is worse at killing things might feel slightly gyped - why is that guy more awesome than me at this thing we both do?

Far as I can tell though, it's a failsafe mechanism, not a necessity. You *could* have two Gunluggers in a game and it wouldn't break it.

If you play what you have and it looks like there's a problem, you could either make sure there's niche protection in a different way (a bunch of different kinds of Stalker moves for everyone to pick), or that niche protection doesn't matter at all - because, say, cooperation and not the actions of a single individual are what's important.

Niche protection could be created (to some degree) through a couple other methods:

1) If there were a nice big list of moves and no character could choose a move already taken by another.  Mini-specializations, as it were.

2) The setting lets players differentiate their characters through the Secrets that they know.  Suppose three characters are fairly similar in general aptitude and skill, but one of them knows about dealing with mutants, one of them knows a safe path through a particular deadly location, and the third knows how to bypass the Brain Scorcher.  The three of them together are capable of slipping past the mutant nests, through the dangerous location, and past the Brain Scorcher to find the treasure beyond.  They're each vital to the success of the expedition, because they know Secrets the others do not.  It's a degree of niche-protection, though not as concrete as discrete playbooks.

Something else I've thought about is voluntarily surrendering your niche-protection.  Suppose your character knows some Secret that the crew will need to deal with some hazard.  Do you keep it to yourself, pissing them off but ensuring that they need to keep you safe until your knowledge is required?  Or do you share that Secret, improving the odds of the crew's success but making you personally less necessary and degrading the value of your hard-won Secret by spreading it around?

TL;DR Niche protection could be maintained by emplasizing what you know instead of what you can do.

"The Regiment" is like this if you play with the special forces playbook, 'The Operator'.  Operators.  Our characters felt very unique, but it was a one-shot, so there wasn't much advancement.  As I recall, too, at least one character was allowed a move out of another playbook.